Project Summary/Abstract Binge alcohol drinking, the most common form of excessive alcohol consumption, contributes to a host of long- term negative health consequences, including the development of alcohol dependence. Repeated episodes of binge drinking drive subsequent alcohol consumption, therefore characterizing the neural circuitry underlying this risky behavior is essential to the development of successful pharmacotherapeutic treatments for alcohol use disorders. The bed nucleus of the stria terminalis (BNST) is critically involved in alcohol drinking and stress-induced relapse of drug seeking. The BNST is enriched with neurons that produce and release corticotropin-releasing factor (CRF), a neuropeptide that has also been shown to regulate these behaviors. During the K99 phase of the grant, we showed that the activity of BNST CRF neurons feed-forward drives binge alcohol drinking using an in vivo chemogenetic approach (Pleil et al., 2015; Rinker et al., 2016). We hypothesize that the activity of this critical neuronal population is highly driven by direct glutamatergic synaptic inputs and that repeated episodes of binge drinking dysregulate BNST CRF neuron function by enhancing the activity of these glutamatergic input neurons. During the K99 phase, we identified and functionally characterized a dense, monosynaptic glutamatergic synaptic input from the paraventricular nucleus of the thalamus (PVT) to BNST CRF neurons. Further, we found that glutamatergic neurons in the PVT also drive binge drinking behavior and that there is plasticity in BNST-projecting PVT neurons following multiple cycles of binge drinking. The goals of the R00 phase of the grant are: 1) to characterize the causal roles of BNST CRF neurons and the PVT-BNST projection in binge alcohol drinking behavior in mice using in vivo optogenetic and chemogenetic approaches, and 2) to examine how BNST CRF neurons and their PVT glutamatergic synapses are altered by repeated cycles of binge drinking using combined ex vivo optogenetics and slice electrophysiology. These studies during the R00 phase will integrate my expertise in slice electrophysiology and behavior with training during the K99 phase in in vivo optogenetics and chemogenetics to thoroughly characterize how crucial nodes of circuitry that regulate binge alcohol drinking are altered by repeated binge alcohol drinking, which may reveal pharmacotherapeutic targets for the treatment of alcohol use disorders.